Method for preparing dental restoratives



. Nov. 3, 1936. F, M YER 2,059,262

METHOD FOR PREPARING DENTAL RESTORATIVES Original Filed May 51, 1952 Patented Nov. 3, 1936 UNITED STATES PATENT OFFICE METHOD FOR PREPARING DENTAL RESTORATIVES Frederick S. Meyer, Minneapolis, Minn.

2 Claims.

This invention relates to a. new and improved method for preparing dental restoratives including bridges and dentures.

It is an object of my present invention to provide a comparatively simple, highly accurate method for making or preparing bridges and dentures for edentulous or partially edentulous mouths to secure balanced and functional occlusion.

With methods and technics extensively utilized at this time for preparing both bridges and dentures, occlusion has been more or less guess work and has been-approximated only by the use of complicated articulators and highly specialized technic for taking the bite and then by spot grinding the bridge or dentures, as the case may be, in the mouth, with too often the result that the bridge or denture did not function right when put to the real test in mastication. With such methods, finger skill, the personal equation and good guess work have been the main factors in producing successful results and an approximate functional occlusion.

It is a further object of my invention to provide a method or technic of the class described wherein all possible movements of the patients mandible are taken advantage of to determine the true functional and balanced occlusal path upon a model; wherein conventional types of articulators are dispensed with; and wherein, in bridgework, no soldered joints are required between the teeth, but the entire bridge is integrally cast andwill accurately fit the abutments and obtain true and balanced functional occlusion.

My improved and new method accomplishes the results above set forth without requiring any substantial amount of finger skill and it eliminates the personal equation. In said method the human jaw is utilized as the articulator and with it the exact position, outline, curves and facets which are necessary to meet all positions of the opposing teeth with every movement of the mandible are obtained.

These and other objects and advantages of the invention will be more fully set forth in the following description made in connection with the accompanying drawing, in which like reference characters refer to similar parts throughout the several views, and in which:

Figs. 1 to 14 inclusive illustrate the principal steps in my method as applied to the preparation of stationary dental bridges.

Referring first to my method as applied to the preparationof a stationary bridge, the abutment teeth are first prepared in conventional manner to receive the abutments.

My next step is to obtain accurate impressions of the abutment teeth and in this connection I prefer to first take a quick impression which may 5 be done in the manner illustrated in Fig. 1 by the use of a thin copper cap or band filled with suitable impression material, such as wax. The cap 3i? illustrated is of substantially greater size than the abutment tooth and as shown, is provided with a loop or string 30a to facilitate removal of the cap and impression material from the tooth. My object in taking this impression is merely to get an approximate reproduction of the abutment tooth. From the impressions taken, temporary dies 3| (see Figs. 2 and 3) are cast from any suitable die material and said temporary dies are utilized to obtain wax patterns 32 for the preparation of suitable substantially rigid impression trays. The wax pattern is purposely made with overhanging margins 32a and is invested in the conventional manner, as shown in Fig. 4 to form a mold, care being taken that the sprue former is aligned with the line of withdrawal of the wax pattern. The mold so formed is then cast, preferably with silver, as illustrated in Fig. 5 to form a suitable tray 33 for taking the impression of one of the abutment teeth. The excess button of the casting of the tray is left on for a handle and the cavo surface of the silver tray 33 is ground out to fit loosely upon the abutment tooth.

With silver trays 33 prepared as above described, impressions 34 are taken upon the abutment teeth. The trays are filled with modeling compound of a nature which will soften with heat 35 and are pressed snugly to place upon the prepared ends of the abutment teeth. I take the trouble to make special cast trays in order that requisite rigidity and proper shape may be obtained to prevent distortion of the impression and producing an impression which will accurately fit the tooth. Furthermore, by making a special tray to approximately conform to the shape of the tooth, only a very small amount of impression material need be utilized. The danger of distortion from thermal changes of the impression is therefore minimized. The thickness of the material of the trays furthermore retains the residual heat and enables a more accurate impression to be taken.

My next step is to prepare from the impression numbered 34 made in tray 33, a suitable amalgam die. A form is prepared for the amalgam die and to this end I prefer to utilize a hollow pyramid for forming the root end of the die, which pyra- 55 mid may be of impression material conveniently formed by shaping a sheet of said material about a tapered rod, as illustrated in Fig. 7. The pyramid 35 so formed is next connected, preferably by wax, with the exterior of the tray 33 having the impression therein, as illustrated in Fig. 8. Care is taken to axially align the pyramid as nearly as possible With the sprue portion of the tray 33.

An amalgam die is then formed in the pyramid and mold formed by the impression of the tray and in filling the pyramid and tray with amalgam I prefer to first invest the joined tray and pyramid externally with plaster, as shown in Fig. 9, to prevent distortion when the amalgam is packed. The pyramid and tray are then filled with amalgam and when the amalgam hardens, the plaster and pyramid are cut away. The die is then carefully removed from the tray without distorting the wax impression formed therein and I prefer to do this by grasping the tray with the fingers in such manner as to cover most of the tray and heating the root of the amalgam die with hot water and then pulling the tray and die apart longitudinally before any substantial amount of heat is transmitted to the impression.

My next step is to make a plaster cast or model of the case and to this end the silver trays containing the impressions are carefully placed upon the abutment teeth in the mouth, as shown in Fig. 10. A plaster impression P. I. is then taken in the mouth, of the teeth and tissues surrounding the mounted trays, and said trays, in taking the impression, remain embedded in the plaster. To assist in taking this impression, a conventional U-shaped impression tray T may be utilized. The embedded trays 33 remain in the impression P. I. taken; and are utilized subsequently for properly locating the amalgam dies 36 in the cast or plaster model to be made. After the plaster impression has hardened and has been properly cut and trimmed the amalgam dies 36 are inserted in the embedded silver trays 33 and the roots of the dies are embedded in plaster and a plaster cast M made from the first mentioned plaster impression (see Fig. 11). This is done by pouring a plaster model, building up the sides of the plaster impression with wax before pouring. The plaster impression P. I. may then be discarded inasmuch as I now have a duplication in the plaster cast or model M, this cast duplicating the surrounding teeth and tissues and the abutments being duplicated by the amalgam dies which are embedded in the cast.

I next build up a small mold or matrix around the dies on the plaster cast (not shown) with base plate or suitable impression material and then pour low fusing metal to make a bridge adjoining the two dies. It is essential that this low fusing metal bridge fulfill the following conditions:

First, it must rest immovably upon the dies. Secondly, it must not touch any of the opposing teeth when placed on the abutments in the mouth. Thirdly, it must have a broader surface than the finished bridge. Fig. 12 shows construction and application of this low fusing metal bridge.

The next step is an extremely important one and consists in obtaining the true functional occlusal path for the bridge model. I take the low fusing bridge 37 and cover the broad ocolusal surface thereof with warm relatively soft wax and place the bridge on the abutments in the mouth (as diagrammatically illustrated in Fig. 13). I then require the patient to go through all possible movements of the mandible, biting or putting The low fusing bridge with the wax tracing thereon is then taken out of the mouth and replaced on the dies in the plaster cast. A plaster cast is then poured into the tracing with definite seating on each end of the first mentioned plaster cast M. The last mentioned plaster cast or model 38 as shown in Fig. 14 is made by setting up the model containing the amalgam dies in a straight line or hinged articulator, of the type shown in Fig. 14. In pouring the last mentioned plaster model or cast 38, properly termed the bite, the upper attachment or hinged elements of the articulator is embedded in the plaster.

Wax patterns are then prepared on the abutment portions of the amalgam dies and porcelain facings F are adjusted approximately to place on the plaster cast between the abutments and the patterns and the facings are tied together with wax, as shown in Fig. 14. These are then read-- justed for alignment and expression on the abut-- ments in the mouth. They are then replaced on the dies and a matrix of plaster is poured to hold the position of the porcelain facings. Before the wax pattern for the bridge is removed the facings are removed. The final tacking together of the different abutment patternsis preferably done at a temperature of 50 degrees F. Between every abutment there is one opening and this opening is not closed until a temperature of 50 degrees F. is obtained. The wax pattern for the bridge is now completed on the model or casts M and 38, see Fig. 14, so that the occlusal surface conforms to the functional occlusal path X on the plaster impression or model 38. On the straight line articulator, see Fig. 14, the occlusal surfaces of the several abutment patterns as well as the occlusal surfaces of the spanning and other portions of the bridge are accurately reproduced from the occlusal path X of the upper model 38.

The model, dies, wax pattern and all are now immersed in water at a temperature of 50 degrees F. and allowed to remain there until they all assume the said temperature. They are then quickly removed and the surface dried and the final opening between abutments is waxed together at this temperature and the whole thing immediately replaced in the water at 50 degrees F. From time to time it is removed and one facing after another taken out. When the facings are all removed and the bridge finally tacked together at a temperature of 50 degrees the wax pattern is then removed from the dies and mounted upon a conventional crucible former where it is invested, using the same technic as we use for investing an ordinary crown. The mold formed by so investing the wax pattern is then cast integrally and the finished casting or bridge will fit accurately to place on the abutment teeth, the margins fitting accurately and the functional occlusal path or occlusal surface of the bridge will be substantially perfect and properly balanced. None of the opposing cusps can interfere in any position of the mandible since the said occlusal surface has been prepared or constructed from a model or tracing formed by causing the patient to go through all the possible movements of the mandible, pressing the opposing teeth against the wax covering or tracing surface.

From the foregoing description it will be seen that by forming a special substantially rigid tray 33 for each of the abutment teeth very accurate and undistorted impressions of the abutments are obtained. It will next be seen that the rigid or silver trays 33 with the impressions of the abutments therein are embedded in a plaster impression or cast, see Fig. 10, in precisely the same relation as the abutments in the mouth, since the plaster is actually poured or impressed with the trays in place upon the abutments in the mouth. It will next be seen that from the said plaster impression with the trays embedded therein the amalgam dies 36 are set up in the plaster model, see Fig. 11, in precisely the same relationship that the abutment teeth have in the mouth. The low fusing metal bridge 31 is then constructed to precisely fit the prepared abutment dies on the cast and the true balanced and functional occlusal path is reproduced on the wax coating covering the occlusal surface of the low fusing bridge. It will, therefore, be seen that substantially perfect bridges may be prepared having true functional and balanced occlusion and that further guess work, the personal equation and subsequent grinding are eliminated.

It will, of course, be understood that various minor changes may be made in the steps and sequence of steps of the method without departing from the scope of my invention which, generally stated, consists in a method capable of carrying out the objects herein set forth, such as disclosed and defined in the appended claims.

What is claimed is:

1. The method of preparing dental restoratives, such as bridges, which consists in making accurate impressions of the abutment teeth, making amalgam dies from said impressions, including elongated root portions, making a substantially rigid model with said amalgam dies positioned therein in the same relation as the abutment teeth in the mouth, making a model or trial bridge which accurately fits said dies, covering the occlusal surface of said model bridge with relatively soft impression material, placing the trial bridge accurately upon the abutments in the mouth and generating by various mandibular movements of the patient a true functional occlusal path on the soft covering of said trial bridge while the patients muscles of mastication are under working pressure, taking an impression in substantially rigid material from the functional occlusal path on the covering of said trial bridge, preparing a wax pattern for the bridge to be produced and forming the occlusal surface of said pattern from thelast mentioned impression and constructing the bridge in conformance with said wax pattern.

2. The method of preparing dental restoratives such as bridges which consists in first making individual rigid impression trays one conforming substantially to the shape of each of the abutment teeth, making accurate impressions of the abutment teeth in said rigid trays, making amalgam dies from said impressions and forming said dies with elongated root portions substantially axially aligned with the impressions, placing said trays with the impressions therein upon the abutment teeth in the mouth and taking plaster impressions of the portions of the tissues and the teeth surrounding the abutment teeth and embedding the trays in the plaster utilized for the impression, inserting the dies accurately in the impression contained in the embedded trays and making a plaster model from said impression and thus positioning the roots of the dies in the cast or model in precisely the same relation as the abutment teeth in the mouth, making a model or trial bridge which accurately fits the dies, said bridge having a relatively broad occlusal surface, covering the occlusal surface of said model bridge with relatively soft impression material, placing the trial bridge accurately upon the abutments in the mouth and shaping and molding by the various mandibular movements of the patient a true functional occlusal path on the soft covering of said trial bridge while the patients muscles of mastication are under working pressure, taking an impression in rigid material from the functional occlusal path on the covering of said trial bridge, preparing a wax pattern for the bridge to be produced, the occlusal surface of said pattern being formed from the functional occlusal path made from said last mentioned impression, said pattern including cavo surfaces to accurately fit the abutments and casting the bridge integrally in a mold prepared from the wax pattern.

FREDERICK S. MEYER. 

